Multi-Species Marine Traps
Used Aquaculture & Processing Machinery
Fukui's Monthly News Letter
Transforming mussel culture
In the past 24 months we have done an extensive survey of the cultured mussel industry, from around the world. A summary of our findings includes the following:
Growout techniques are very diverse depending on site specifics, species, labour culture market, and the individual goals of growers;
Mussel culture is being done by a variety of businesses from part-time growers, to family operations that depend on mussels for their total income, to larger corporations that are very production oriented; and
When it comes to production and efficiency the current benchmark has been set by the New Zealand industry and its mechanization. Bottom culture is at the other end of the production scale. This statement is based on the three rules of commercial grow-out as well as maximizing the "cubic" meters or yards for the lease instead of the "square" area.
Though bottom culture continues to be the method by which the largest volume is produced worldwide, hanging culture methods using the total water column produces more mussels per given area. Hanging culture mussels also tends to be a better quality product - free of sand and grit, and providing a better yield.
Prince Edward Island (PEI), Canada growers have shown that their cultured mussel deliver twice as many mussels per pound (due to the higher shell weight of bottom grown), as well as meat yields that are usually 3 to 4 times higher than wild.
While in PEI in July one of our colleagues from Germany also confirmed a taste advantage when we feasted cultured mussel at a local restaurant. In his words, "It is the first time I really enjoyed mussel." (German production is bottom harvest only.)
Probably due to the fact that mussels are one of the easiest to grow of all shellfish species, the equipment used for growout - except for New Zealand - is pretty basic.
As an overview, culture is done in socking made of extruded / oriented polyethylene, knitted slit film, dissolvable cotton or acetate wrap / socking on a rope core (New Zealand, Spain) and the very new knitted netting made of polyethylene or super strong polyester fibers.
Deployment styles and methods are wide ranging, from rafts in Spain, bouchots in France (wooden poles with socking wrapped around like a barber pole stripe), to longlines both in submerged and surface applications. Each has its benefits based on the history of the region and the specifics of the sites.
A paradigm shift is taking place in some areas, however as growers look for higher yields with more efficient labour methods.
Since the New Zealand industry sets the standard by which efficiency and productivity are measured, it is important to note that its level of mechanization did not happen overnight and was the result of a number of different manufacturers and individuals working together.
A unique circumstance - the massive collapse in harvest in the early 80s - caused, but also enabled the New Zealand industry to start fresh. They forgot all their old equipment and ideas, and pioneered development of husbandry methods that totally changed the approach to mussel farming. Using the whole water column for hanging growout, mechanization was applied to the process of seed deployment as well as harvest.
With this in mind, we duplicated that team approach and brought together a number of manufacturers to provide a total solution. We identified systems and equipment for upgrading that includes specialized seed collectors, mechanical harvesters, high speed socking tables, declumper / graders, bulk handling systems.
And, the key to making this shift to greater efficiency is the new socking material now available from Fukui North America. Its strength and controlled stretch width enables growers to use single drop lines at greater water depths. Or, with increased mechanization, growout lines can be set in the continuous mode (see diagrams).
Since change usually does not happen quickly, we know that a switch from single dropper to continuous methods would not happen overnight. Therefore all the equipment was designed in a modular plan so that growers had a choice to take one step forward at a time or one sweeping move.
In farm visits, we found some interesting challenges that we were able to solve with the new system.
For example, some growers have seed to mussel conversion ratios of as high as 3:1; that is, you have to plant three of the valuable seeds to produce one mussel. In efficient operations, the ratios are 1.3 to 1.8 for each mussel produced.
Extruded socking with its difficult-to-control stretch width was the cause of the problem. The new socking fixes that.
Another example was with site inefficiency. I was on a site in Newfoundland that could only use the top 12' of the water column with a water depth that was close to 80' with no thermocline.
The limitation was the strength of the socking, which at full grow-out would break in the 12' to 15' range. The new socking material could increase site efficiency, which, as you see in the diagram, increases the grower's profitability.
In upcoming columns I will go into more detail on some of the more advanced methods that are emerging including offshore-submerged systems that change the rules entirely, duck predation solutions, submersible rafts and harvesting machinery.
Contact Don Bishop at:
Fukui North America
110-B Bonnechere St.W.
Eganville, Ontario K0J 1T0
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